Bump to 12.4

Author: rockbruno

.github/workflows/ci.yml

@@ -15,9 +15,13 @@ jobs:
       uses: actions/checkout@v2
     - name: Build
       run: make build
+      env:
+        DEVELOPER_DIR: /Applications/Xcode_12.4.app/Contents/Developer
     - name: Run tests
       run: make test
     - name: Check the example project
+      env:
+        DEVELOPER_DIR: /Applications/Xcode_12.4.app/Contents/Developer
       run: cd ./ExampleProject && make swiftshield
     - name: Try to package it
       run: make package